Block:AFE Gm-C
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AFE — Gm-C integrator front-end
AC-coupled low-noise front-end built from a transconductance (Gm) stage driving an integrating capacitor, followed by a switched-cap LPF (SC LPF). Sits on top of electrode DC offset and electrochemistry.
Design equation
Mid-band gain: <math>A_v = G_m \cdot R_{out}</math> High-pass corner set by the pseudoresistor network (AC coupling) — see bias / pseudoresistor notes.
Known failure modes
- DC offset overloading the input pair.
- Pseudoresistor corner drifting with process (weak-inversion resistor).
- Gm nonlinearity at large offsets.